Heated propagation bench questions

Hello,I'm getting electricity to my small polytunnel for the first time and want to set up a heated bench of some sort for germinating veg seeds and growing on tender plants..Just at the initial planning stages & looking at the basics. Such as whether to go for wet sand/soil warming cable or for heated mats. Would either of these be better with capillary matting? Grateful to hear any tips/experiences with heated benches please,Thanks, c&w